1. Field of the Invention
The present invention pertains, generally to the field of permeable membranes and packaging for volatile materials, such as fragrances and other aromatic products, and more particularly, to permeable multilayer membranes and packages, which allow the controlled release of aromatic products over a period of time. The package prevents the escape of the aromatic fragrance until the consumer desires to start the release of the fragrance by peeling back the package to expose the permeable membrane.
2. Description of the Art
The controlled time release of very volatile substances, such as fragrances and other aromatic products, presents a number of packaging problems. Room xe2x80x9cair freshenersxe2x80x9d or fragrances have usually been packaged in glass bottles or vials. The fragrance is released into the atmosphere by transmission through an absorbent wick, which is capped until the time of use. However, glass bottles are bulky and breakable. It is generally not economical to package fragrances in small quantities inside glass containers, because the cost of the glass container is high.
One proposed alternative method of packaging room fragrances is to place a breakable glass vial within a plastic container formed of a material that is permeable to the vapors of the volatile fragrance. The user deliberately breaks the glass vial to allow the fragrance liquid to seep into the absorbent pad and the vapors from the liquid slowly diffuse into the atmosphere through the permeable outer container. These containers may be subject to accidental breakage of the glass vial during shipping and handling, as well as to a possible puncture of the container by broken glass. The manufacturing costs are increased by the use of the glass vial within the container.
Other fragrance dispensers utilize sealed packages, which are opened by peeling back a covering foil to expose a perforated panel covering an absorbent pad filled with the fragrance liquid. The costs of such containers make them generally inappropriate for dispensing small amounts of the fragrance. It is also somewhat difficult to obtain controlled release of the fragrance at a fairly constant rate over the life of the product, because the liquid is directly exposed to the atmosphere. In addition, the consumer may come into contact with the fragrance liquid, because the fragrance liquid may seep through the holes in the perforated panel.
Many other common packaging materials, including some plastic films, are permeated by the fragrance before the desired release or are subject to attack by the fragrance itself or by its liquid carrier.
U.S. Pat. No. 4,634,614 issued to Holzner, relates to a peel system for a device for perfuming ambient air. The peel system comprises a delamination of a paper layer to separate a non-permeable lidding from a permeable membrane. In this invention, the paper layer does not provide a barrier to the aromatic product and some of the aromatic product is allowed to escape with time. In addition, the exposed membrane often has a poor appearance, as paper fibers may be left on the membrane when the package is peeled to activate the fragrance.
U.S. Pat. No. 4,145,001 issued to Weyenberg et al., and incorporated herein by reference, discloses a dispenser having a permeable membrane. The fragrance is sandwiched between the inner layers of two heat sealable panels. One of the inner layers is permeable to the fragrance vapors. The outer layers of the panels are impermeable to the fragrance and its vapors. The dispenser is opened by peeling back a panel along a release layer to expose the inner permeable layer. However, the permeable membrane layer disclosed in U.S. Pat. No. 4,145,001 has limited permeation for certain fragrances.
Other problems associated with permeable membranes are problems with machine operations. The most effective resins for permeation are often tacky in nature. The tacky nature of these resins often cause problems with the operation of the package machinery and processing steps, such as laminating, slitting and converting.
One objective of the present invention is an improved permeable multilayer membrane that provides greater controlled release over an extended period of time and increased permeation for a broader range of fragrances. Another objective is a multilayer membrane, which allows for the special selection of resins in the machine and tie layers to prevent problems associated with the operation of the package machinery and processing steps. Another objective of the present invention is to provide packaging for the fragrances and a means for exposing the membrane to the atmosphere at a desired time by consumer manipulation. A still further objective is to provide a release layer that has improved barrier to fragrances.
This invention relates to an improved permeable membrane for volatile substances, such as a room air fresheners, fragrances and other aromatic products, that satisfies the need for a permeable membrane which provides greater controlled release and increased permeation for a broad range of fragrances. This invention also relates to the packaging of the improved permeable membrane and to provide a means for exposing the membrane to the atmosphere at a desired time by consumer manipulation. This invention also relates to an improved release layer that aids in containing the fragrance until the packaging is opened.
In one embodiment of the present invention, the invention is a coextruded multilayer structure comprising a permeable membrane and a release layer. The membrane comprises a first permeable sealable layer, a second permeable layer. The release layer is adhered to the second layer. The adhesion between the release layer and the second layer is a relatively weak bond compared to the bond between the first and second layers. The bond strength is controlled by the selection of the resins in the second layer and the release layer.
The first layer includes polymers, such as polyethylene, poly(ethylene vinyl acetate) (EVA) and other heat sealable permeable resins. The second layer includes polymers such as polyethylene, poly(ethylene vinyl acetate) and others that can be blended or modified to produce a strong bond to the first layer and a relatively weak bond to the release layer. The release layer includes a polymer or copolymer such as nylon or ethylene vinyl alcohol copolymer (EVOH).
The ethylene vinyl alcohol of the present invention has a ethylene content of less than forty percent. The nylons of the present invention include poly(xcex5-caprolactam)/nylon-6; and poly(hexamethylene)/nylon-6,6.
In another embodiment of the present invention, the invention is a coextruded multilayer structure comprising a permeable membrane and a release layer. The membrane comprises a first permeable sealable layer, a second permeable layer adhered to the first layer and a third permeable layer adhered to the second layer. The release layer is adhered to the third layer. The adhesion between the release layer and the third layer forms a relatively weak bond as compared to the adhesion between the first and second layers and the adhesion between the second and third layers.
The first layer includes a polymer, such as polyethylene, (poly(ethylene vinyl acetate) (EVA) and other heat sealable permeable resins. The second layer comprises semi crystaline polymers. The third layer is selected from resins that provide a high (strong) degree of bond to the second layer and controllable relatively weak bond to the release layer. The release layer includes a polymer, or copolymer such as nylon or EVOH resins.
In another embodiment of the present invention, the invention is a coextruded multilayer structure comprising a permeable membrane and a release layer. The membrane comprises a first permeable sealable layer, a second permeable layer adhered to the first layer, a third permeable layer adhered to the second layer and a fourth permeable layer adhered to the third layer. The release layer is adhered to the fourth layer. The adhesion between the release layer and the fourth layer forms a relatively weak bond as compared to the adhesion between the first and second layers, the adhesion between the second and third layers and the adhesion between the third and fourth layers. The release layer also cooperates with the impermeable layers to contain the product.
The first layer includes a polymer, such as polyethylene, EVA blends including very low density polyethylene (VLDPE) and other heat sealable resins. The second and fourth layers are selected from resins that provide a high degree of bond to the first and third layers and a controllable relatively weak bond to the release layer. The third layer comprises resins with high permeability to gases and aromatic compounds. The release layer includes a polymer, such as a homopolymer or copolymer of nylon or EVOH.
In another preferred embodiment of the invention, the coextruded multilayer structure is incorporated into a package. The package holds an aromatic product between two heat sealable panels. One of the panels can be manipulated to remove certain impermeable layers to expose a permeable membrane to the atmosphere, which allows for the escape of the vapors from the aromatic product.
The first heat sealable panel is a laminated structure. It comprises a permeable membrane, a release layer and an impermeable portion. The permeable membrane comprises a first permeable sealable layer, a second permeable layer adhered to the first layer and a third permeable layer adhered to the second layer. The release layer is adhered to the third layer of the permeable membrane. The release layer is relatively impermeable to most products and cooperates with the impermeable layers to contain the product.
The impermeable portion comprises one or more impermeable layers and is selected to be impermeable to the aromatic product and its vapors, so that no significant amount of vapors will escape while the package is sealed. The impermeable portion is laminated to the release layer opposite the permeable membrane.
The second heat sealable panel is a laminated structure comprising one or more impermeable layers, which are selected to be impermeable to the aromatic product and its vapors, so that the vapors will not escape while the package is sealed.
The aromatic product is disposed between the first sealable layer of the membrane in the first heat sealable panel and an outer layer of the second heat sealable panel. The first sealable layer of the membrane and the outer layer of the second panel are heat sealed together in a bond formed around the aromatic product.
The heat bonding around the aromatic product is preferably accomplished by pressing all of the layers of the package between a hot die and a resilient backing. In such a case, the release layer of the first heat sealable panel is selected of a material which will form only a weak heat bond with the third permeable layer of the membrane. The adhesion of the weak heat bond is substantially less than the adhesion of the bond between the second and third layers of the membrane and the first and second layers of the membrane. The adhesion of the bond is also less than the adhesion of the bond between the first sealable layer of the membrane and the outer layer of the second panel.
Preferably, the first sealable layer of the membrane and the outer layer of the second panel are not adhered together, except at the heat bond area. This allows the layers of the package to be easily pulled away from each other by the user between the two heat sealable panels up to the area of the bond. As the package is pulled by the user to the area of the heat bond, the first sealable layer of the membrane will split at the heat bond and remain bonded to the outer layer of the second panel. The release layer will part from the third layer of the membrane to allow the release layer and the impermeable layers of the first heat sealable panel to be removed. This leaves the aromatic product covered on one side by only the permeable membrane and allows the vapors from the aromatic product to diffuse through the permeable membrane into the atmosphere at a fairly constant rate over a period of time.
The process of heat bonding the layers of the package together is preferably accomplished by using a die having a lip or protrusion extending slightly beyond the face of the remainder of the die. When such a die is pressed onto the package layers and against a resilient backing, the first sealable permeable layer of the membrane and the outer layer of the second panel will soften and spread apart from the line of the protrusion on the die to form a line of weakness. This line of weakness is advantageous in allowing the membrane to split easily as the package is peeled open by a user. To ensure the structural integrity of the package, it is preferable that the impermeable layers are formed of a material which will not melt at the temperature of the bonding die.
For optimum performance of the package, it is also preferred that the line of weakness, and the wider heat bond adjacent to it, be formed in a V or a chevron shape at a position spaced away from one end of the package. The user easily peels open the package up to the point of the chevron, with the weakened permeable layers splitting at the chevron to allow the remainder of the package to be peeled apart. The remainder of the heat seal surrounding the aromatic product is sealed over a broad area without forming a line of weakness.
The package of this invention has the desirable feature of being relatively light and has no breakable parts, which could be dangerous. The package is very inexpensive to manufacture and is suitable for dispensing small quantities of fragrances. As long as the package remains sealed, the volatile fragrance cannot escape; thus, allowing a very long shelf life for the product. Special precautions during the handling of the product are unnecessary, since there are no parts that can be broken or easily damaged. Once the package has been opened by the consumer, the volatile vapors diffuse through the permeable membrane at a controlled and selected rate. Because the process of transfer through the permeable layer is a diffusion process, rather than direct evaporation, the rate of release of the vapor is relatively uniform over the expected life of the package.
In a preferred process for producing the package, the layers of the permeable membrane and the release layer are cast coextruded to form a very uniform but weak bond between the membrane and the release layer. The impermeable portion of the first panel is then adhered to the release layer using an adhesive, which provides a long lasting and uniform bond between the two materials. The two heat sealable panels may then be brought together over the aromatic product with a heated die being impressed over the two panels of the package to form a heat bond between them that surrounds and seals the aromatic product. Various materials, such as metal foil, may be used for the impermeable portion, and in such case it is desirable to protect the outer surface of the foil layer(s) by adhering a tough protective layer thereto.
In the case of some aromatic products the release layer can be selected to have sufficient barrier to the product to eliminate the need for foil or other high barrier layers in the non-permeable portion of the top panel. The panel is typically constructed with reverse printed polyethylene tertphthalate (PET) film as the outer most layer. A barrier layer located between the permeable membrane layers and the printed surface is required not only to contain the produce prior to use but dually protects the printing from product attack. The barrier requirement is a function of the chemical formulation of the product and the required shelf life prior to use. Certain products contain fragrance oils or carriers such as iso-par that permeate more readily than other formulations and thus require greater barrier. This is particularly true if the product must be contained for 1-2 years before use.
In another preferred embodiment of the present invention, the coextruded multilayer structure is incorporated into a package. The package holds an aromatic product between two heat sealable panels. A first heat sealable panel can be manipulated to remove certain impermeable layers to expose a permeable membrane to the atmosphere, which allows for the escape of the vapors from the aromatic product. The first heat sealable panel comprises a four layer permeable membrane, a release layer-which is somewhat impermeable and an most impermeable portion. The impermeable portion comprises one or more impermeable layers. The permeable membrane comprises a first permeable sealable layer, a second permeable layer adhered to the first layer, a third permeable layer adhered to the second layer and a fourth permeable layer adhered to the third layer. The release layer is adhered to the fourth layer of the permeable membrane and the, impermeable portion is laminated to the release layer opposite the permeable membrane.
A second heat sealable panel is a laminated structure comprising one or more impermeable layers, which are selected to be impermeable to the aromatic product and its vapors, so that the vapors will not escape while the package is sealed.
The aromatic product is disposed between the first sealable layer of the membrane in the first heat sealable panel and an outer sealable layer of the second heat sealable panel. The first sealable layer of the membrane and the outer layer of the second panel are heat sealed together in a bond formed around the aromatic product.
In another preferred embodiment of the invention, the second heat sealable panel comprises a thermoform tray. The first sealable layer of the membrane is heat sealed to the thermoform tray to cover the tray.
These and other features, aspects and advantages of the present invention will be apparent from the following detailed description, appended claims and accompanying drawings showing preferred embodiments of the present invention.